In the field of surgery, two general methods of accessing a site within a patient's body are used. In open surgery, the patent is anesthetized, commonly with general anesthesia, and the surgeon then makes a relatively large incision in the patient. The location and size of the incision will, of course, depend on the organ or tissue to be treated, as well as the disease, injury, or other abnormality of such tissue. After the incision is made, the surgeon retracts the skin, muscle, fatty tissue, bones, or other tissue that lie between the incision and the treatment area or that otherwise hinder the surgeon's access to such area. The surgeon can then view the tissue to be treated, for example the heart, and can directly approach that tissue with surgical instruments. At this point, a surgeon may have to impede or stop the function of the organ or tissue to be treated. Most commonly, that step is necessary in order to prevent movement of the organ or tissue, or to prevent fluid flow into or out of the organ or tissue. Again using the heart as an example, open-heart surgery requires the surgeon to connect the patient's circulatory system to an external machine (a "heart-lung machine," or in the surgeon's vernacular a "pump"), and to induce cardioplegia. With the patient's blood routed around the heart and the heart muscle itself stationary, the heart surgeon can then enter the heart and perform the necessary operation.
The principal advantage of such open procedures is the comparative ease of access to the organ or other tissue to be treated. The organ or other tissue is substantially exposed to operating theater conditions, providing ample light on and space around the tissue, and aid the surgeon in performing the procedure. A significant disadvantage, however, is the necessity of stopping the function of the organ or tissue. In such cases, the risks of ischemic or other damage or irritation to the organ resulting from discontinuing of the organ's function organ are substantially heightened. Additionally, there is the risk that the organ or tissue will not restart its function or will restart only partially. In heart surgery cases, for example, other risks such as the risk of emboli being introduced into the vascular system is also increased. Further, the damage to tissues that are retracted or proximate to the incision in such open surgical procedures, and their concomitant discomfort and relatively long healing term, are also disadvantages of open surgical procedures.
The second general method of performing internal surgery is via intravascular or percutaneous minimally-invasive procedures. Using non-invasive measures such as x-ray, ultrasound, or other techniques or procedures, it is frequently unnecessary to expose the internal tissues of patients in order to diagnose or treat medical problems. Once a disease, injury, or abnormality has been non-invasively detected, one or more small incisions are made through the patient's skin, either in the neighborhood of the problem to be treated or to gain access to a relatively large blood vessel, such as the femoral vein. Specially-developed thin and commonly flexible instruments can then be inserted into the patient through the incision, maneuvered into position and the tissues can be treated using such instruments. Some procedures may be performed by observing the motion of the instruments relative to the tissues under fluoroscopy. In other procedures, a flexible observation device or endoscope may be inserted through an incision, and a view of the tissues to be treated may be obtained through the endoscope. When the procedure is completed, the instruments are withdrawn and the small incision(s) are closed.
Again taking the heart as one example, in the case of minimally-invasive heart treatments, a catheter may be introduced into a blood vessel percutaneously. The catheter can then be advanced under fluoroscopic observation within the blood vessel toward and into the heart. At that point, medication may be administered, or instruments and/or implants may be advanced through the catheter and utilized within the heart. Alternatively, as indicated in U.S. Pat. No. 5,797,960, a small thoracic incision can be made, and a cannula inserted through the small incision and a substantial portion of the chest and into the heart. Minimal-diameter instruments or implants can be advanced through the cannula and into the interior of the heart for employment.
Such minimally-invasive techniques have several advantages. First, the organ or tissue to be treated need not be stopped or impeded in order to treat it using such procedures. Additionally, because smaller incisions are used and there is less need for retraction of tissues proximate to the incision, there is less overall trauma and scarring to the tissues involved. Thus, a significant portion of the risks associated with currently-known open surgical procedures is not present with minimally-invasive procedures. Nonetheless, there are several disadvantages to minimally-invasive procedures as well. The principal disadvantage is the lack of direct access to and visualization of the organ or tissue that requires treatment. Minimally-invasive procedures are generally not directly observable, due to the small profiles of cannulas, catheters, and incisions used in such procedures. Fluoroscopic techniques provide some indirect view of the treatment, but generally produce an image that is not very sharp or exact. Insertion of an endoscope can provide a somewhat sharper image, but such instruments have a limited field of vision and must provide light by which to see. Therefore, both the observation end and the light source must be focused relatively closely on a certain area of tissue, and may interfere with treatment of the tissue.
What is needed, therefore, is a device and method for minimally-invasive use in surgical procedures that allows direct access to and visualization of an organ or tissue needing treatment, but that does not require the stoppage or impedance of function of the organ or tissue. Such a device should incorporate the advantages of minimally-invasive surgery, in that it minimizes tissue trauma as well. The devices should be useful in one or more organs, but should particularly be useful in the heart, in which open surgeries necessitate stopping the heart, and in which minimally-invasive surgery may not adequately correct the problem.